Television broadcasting standards require that the transmitted signal parameters such as video gain, sync amplitude, burst amplitude, chrominance/luminance gain ratio, setup level, and burst phase be maintained within specified limits. As the transmitted signal consists of the carrier, the upper sideband, and the lower sideband, all three of which are superimposed on one another with the resultant indicated, means to detect the transmitted signals are required; means include precision tunners, demodulators, etc., all of which are well-known by those skilled in the art. Once the transmitted signal has been detected it is possible to monitor and determine the above mentioned signal parameters, hence maintain these parameters within the specified limits. However, no means has been provided to automatically maintain the signal parameters because of the difficulty in providing a reference from the demodulator which is of known timing.
The present invention overcomes the above mentioned difficulty by providing a reference from the demodulator which is of known timing by developing a drive pulse directly synchronized to the demodulated video thus causing the demodulator to provide the reference which has known timing.
Further, a vertical interval reference signal is inserted in a particular line during the vertical interval having all the required signal parameters as set forth above so that a percentage comparison between the reference from the demodulator and the inserted signal develops a control signal to automatically maintain a uniform transmitted signal which has heretofore been maintained uniform by manual means.